The present invention relates to improvements in electrical actuation of fluid-control valves to enhance responses which tend to be adversely affected by low levels of signals and/or by hysteresis, and, in one particular aspect, to novel and improved arrangements and practices for accurate, efficient and high-speed regulation of fluid flow whereby a solenoid control valve which responds to flowmeter measurements and electrically-characterized settings is so energized that it will develop minute hysteresis-suppressing vibrations and is at critical times automatically over-excited deliberately to stimulate immediate and effective valving action under certain near-zero flow conditions.
There are numerous and varied process-control systems, and the like, in which flow of liquid or gaseous fluid must be sensed and regulated by valving which will establish and maintain a condition characterized in some setting made by an operator or an established program. Control of gases used in complex semiconductor-etching operations involves such sensing and valving, for example, and there the system demands can be especially rigorous because of close tolerances to be observed in fashioning very intricate high-cost product. Solenoid-type valves, in which spring-suspended armature valving members are axially drawn open from seated fully-closed valving positions to extents governed by electrical currents driven through their windings, can be relatively uncomplicated and yet highly-effective devices which tend to be favored for application in such systems. However, such valves can also be sluggish in reacting to low levels of exciting current, particularly when they are to be cracked open from full closure, and the attendant lags can have untoward consequences in situations where exceptional precision and speed of response may be crucial. Moreover, such valves are further prone to exhibit so-called "hysteresis", probably due largely to erratic changes in the mechanics of their spring suspensions, whereby their valving operations in response to excitations are not always exactly the same; as would be expected, the consequences in system performance can be unfavorable on that account as well.